New virus emerges in Malaysia

On Mar. 7, 1999, a 49-year-old pig farmer in
Malaysia developed fever, headache, behavioural
changes, blurred vision and lethargy. On admission
complete blood count, electrolyte levels and a CT scan
of the head were normal. Over the following days he deteriorated
rapidly, with generalized seizures, respiratory failure,
unstable blood pressure and high spiking fevers. He
died 6 days after the onset of symptoms. On
the day of his death, lumbar puncture revealed
a high protein level (2.09 g/L). His
brother, a worker on the same pig farm, had
died a few days earlier from encephalitis.1
Between Sept. 29, 1998, and Apr. 4, 1999,
229 cases of febrile encephalitis were reported
in Malaysia. Patients typically presented
with a 3- to 14-day history of fever
and severe headache, followed by drowsiness
and disorientation often progressing to coma within 24 to
48 hours. Almost half of those affected died. Three clusters
of cases, primarily adult men reporting close contact with
swine, have been identified. Respiratory and neurologic
symptoms and death among swine from the same regions
occurred concurrently. In Singapore in March, 9 similar
cases, 1 of which was fatal, and 2 cases of respiratory illness
occurred among abattoir workers who had handled swine
imported from Malaysia.1
Although Japanese encephalitis virus was suspected at
first, tissue culture from central nervous system specimens
has identified the presence of an agent never previously described.
Electron microscopic studies and preliminary nucleotide
sequencing indicate that the agent is a virus similar
but not identical to another relatively new entity, the Hendra
virus. Hendra-virus IgM antibodies were identified in
the serum of 23 of 26 cases, and Hendra-like antigens have
been detected in tissue specimens from affected swine.1
Hendra virus was first recognized in September 1994 in
the wake of an outbreak of respiratory illness in 20 horses
and 2 humans in Hendra, Queensland, Australia. One man
and 14 horses died.2 An outbreak in Mackay, Queensland, in
August 1994 was later shown to be due to the same virus.3
Although some investigators recommend classifying the
Hendra virus in a new genus, most have described it as an
equine morbillivirus within the family Paramyxoviridae.2,4
Other morbilliviruses include human measles virus and a variety
of viruses pathogenic in animals, including rinderpest,
canine distemper and peste des petits ruminants viruses.2 In
horses, cats, guinea-pigs and humans, the Hendra virus has
been shown to cause vascular lesions in the lungs and other
tissues.5–7 Fruit bats of the species Pteropus poliocephalus are
believed to be the natural hosts.5,8 Although transmission between
species can occur, the virus is not highly contagious,
and transmission from horses to humans through exposure
to infected blood or bodily fluids is rare.5
A variety of new morbilliviruses have emerged in recent
years. Beginning in the late 1980s investigators identified
new morbilliviruses occurring in marine
mammals.3 A recent report has
implicated yet another novel morbillivirus
transmitted by bats in the increased incidence
of stillbirths and deformities among
piglets in New South Wales, Australia.9
Preliminary investigations suggest that
spread of the new Hendra-like virus in
Malaysia occurred through transport of infected
swine.1 Although the presumed
wildlife reservoir and modes of transmission of the virus
have yet to be determined, close contact with pigs seems to
be necessary for human infection. No cases have been reported
among unexposed family members or health care
workers caring for ill patients. To prevent further spread,
transportation of pigs within Malaysia has been banned, and
all people in affected areas who are in close contact with
pigs have been advised to use protective clothing and equipment.
Although travel restrictions have not been imposed,
visitors to Malaysia should be aware of the outbreak.1